“The waking brain is optimized for collecting external stimuli, the sleeping brain for consolidating the information that’s been collected. At night, that is, we switch from recording to editing, a change that can be measured on the molecular scale. We’re not just rotely filing our thoughts — the sleeping brain actively curates which memories to keep and which to toss.”
Everything you ever wanted to know about what happens when we sleep (and even some things you didn’t realize you wanted to know) can be found in this in-depth National Geographic piece.
You’ll get a complete breakdown of what happens in each stage of sleep, why it’s so important, and the impact technology and artificial light have on our sleep habits.